Different bash prompt for different vi editing mode?

Fresh bash 4.3 and readline 6.3 have something for you guys.. from the changelog:

4.  New Features in Readline
j.  New user-settable variable, show-mode-in-prompt, adds a characters to the
    beginning of the prompt indicating the current editing mode.

So putting

set show-mode-in-prompt on

into /etc/inputrc or ~/.inputrc (thx stooj) should affect all your readline-enabled programs 😉